Master cylinder for hydraulic brake systems



Aug. 2, 1949. L A M N R] 2,477,758

MASTER CYLINDER FOR HYDRAULIC BRAKE SYSTEMS Filed May 21, 1945 2 Sheets-Sheetl Fig.2.

To 1 N N INVENTOR.

LUDWIG A.MAJNER| ATTORN E-YS ug. 2, 1949. L. A. MAJNERI 2,477,758

MASTER CYLINDER FOR HYDRAULIC BRAKE SYSTEMS Filed May 21, 1945 2 SheetsSheet 2 INVENTOR.

LUDWIG A. MAJNERI BY W/W M ATTORNEYS Patented Aug. 2, 1949 MASTER CYLINDER FOR HYDRAULIC BRAKE SYSTEMS Ludwig A. Majneri, Grosse Pointe, Micln, assignor to The Warner Aircraft Corporation, Detroit, Mich., a corporation of Michigan Application May 21, 1945, Serial No. 594,942

Claims. (Ci. 60-543) This invention relates to hydraulic braking systems and refers more particularly to an improved type of control unit for use in connection with hydraulic braking systems.

One of the principal objects of this invention is to provide hydraulic braking equipment embodying a control unit having a reservoir for hydraulic fluid medium and having a master cylinder characterized in that it is capable of serving a plurality of brake applying wheel cylinders.

A control unit embodying the above features of the wheel and formed with circumferentially spaced axially extending splines It for slidably supporting a ring II. The periphery of the ring may be successfully used in a hydraulic brake installation where one brake assembly is equipped with a brake having a main brake applying unit comprising one or more brake actuating wheel cylinders operated by an energizing unit also embodying a brake actuating cylinder. In accordance with this invention, the cylinders of both units are independently connected to a single control unit constructed to maintain the optimum fluid requirements in both units under practically all operating conditions and havin means for closing communication to the cylinders in the main brake applying unit before the control unit functions to displace fluid in the energizing unit.

The foregoing as well as other objects'will be made more apparent as this description proceeds, especially when considered in connection with the accompanying drawings, wherein:

Figure 1 is a semi-diagrammatic sectional view of a hydraulic brake assembly embodyin a control unit constructed in accordance with this invention;

Figure 2 is a. fragmentary sectional view showing the brake assembly in connection with a ground engaging wheel;

Figure 3 is a longitudinal sectional view through the control unit shown in Figure 1;

Figure 4 is a cross-sectional view taken substantially on the plane indicated by the line 4-4 of Figure 3; and

Figure 5 is an enlarged sectional view of a part of the control unit.

Upon reference to Figures 1 to 4 inclusive, it will be noted that the reference character l0 indicates a ground engaging wheel, ll indicates a hydraulic brake assembly and I2 designates a control unit. The ground engaging wheel in is of conventional construction and is supported in the usual manner on an axle I3 for rotation about the axis of the axle. As shown particularl in Figure 2 of the drawings, the wheel I0 is provided with a tire carrying rim i4 having an inwardly extending annular portion I5, concentrically disposed with respect to the axis of rotation I1 is formed with correspondingly circumferentially spaced axially extending grooves l8 for respectively slidably receiving the splines it. As a result, the ring ll rotates as a unit with the wheel l0 and is capable of sliding movement in opposite directions axially of the wheel.

Secured to the axle II at the inner side of the wheel III is a main brake applying unit embodying a supporting member l9 having a radially outwardly extending flange 20 positioned at the axially outer side of the ring I! and having a suitable brake lining material 2| secured to the axially inner-side thereof for frictional engagement with the adjacent surface of the ring IT. The supporting member I9 is further provided with a plurality of wheel cylinders 22 at the axially inner side of the ring [1. The number of wheel cylinders 22 may vary in accordance with design considerations but, in the present instance, three cylinders are selected for the purpose of illustrating the invention. As shown particularly in Figure 1 of the drawings, the center cylinder communicates with the adjacent cylinders through the medium of ports 23 and each cylinder has a piston 24 slidably supported therein in the manner shown in Figure 2 of the drawings. A friction disc 25 is secured to the axially outer surface of the head of each piston 24 for frictional engagement with the ring I! upon move ment of the pistons in an axial outward direction. As the friction discs 25 contact the ring II in response to axially outward movement of the pistons 24, the ring I! is moved in a corre; sponding direction into frictional contact with the friction member 2| to apply the brake.

Hydraulic fluid medium under pressure is admitted to the cylinders 22 to operate the pistons 24 by an energizing unit 26. The energizing unit 26 comprises a bracket 21 having an annular portion 28 journalled on the axle ii for rocking movement and having a. wheel cylinder 29 for slidably supporting a piston 30. The piston 30 is supported on the same side of the ring I! as the pistons 24 and has a friction disc 25' secured to the head thereof for engagement with the ring IT. The ring I! is moved axially outwardly by the piston 30 into contact with a friction member 2| suitably flxed to an adjacent portion of the bracket 21. Inasmuch as the ring I! rotates as a unit with the wheel I0, it follows that operation of the piston 30 to apply the brake imparts a rocking movement to the bracket 21 in one direction or the other depending upon the direction of rotation of the wheel. This rocking movement of the bracket 21 serves to apply the main brake actuating unit comprising the wheel cylinders 22. In detail, it will be noted from Figure 1 of the drawings that the member I9 is formed with a pair of cylinders 3| and 32 respectively positioned at diametrically opposite sides of the axis of rotation of the wheel. The upper end of the cylinder 3| communicates with one of the end cylinders 22 through a passage 33 and the upper end of the cylinder 32 communicates with the other end cylinder 22 through a passage 34. Pistons 35 and 36 are respectively slidably supported in the cylinders 3| and 32. The piston 35 is provided with a rod 31 which projects through the lower end of the cylinder 3| and supports a roller 38 for engagement with a cam 39 projecting laterally from the bracket 21. The piston 36 is provided with a similar rod 40 having a roller 4| at the lower end for engagement with a cam 42, which projects from the bracket 21 in a direction opposite the direction of extension of the cam 39.

Assuming that the main brak'e applying unit, including the cylinders 3| and 32, is filled with a hydraulic fluid medium, it will be noted that displacement of fluid in the energizing cylinder 29 applies the brake friction members to the ring I1 and imparts a rocking movement to the bracket 21. Assuming also that the direction of rotation is indicated by the arrow 43 in Figure- 1 of the drawings, it will be noted that the bracket 21 is moved in a corresponding direction. As a result, the cam 39 on the bracket 21 operates through the roller 38 and rod 31 to move the piston 35 upwardly in the cylinder 3|. Fluid is thereby displaced in the cylinder 3| through the passage 33 to effect a displacement of the fluid in the main brake applying cylinders 22. Displacement of fluid in the main brake applying cylinders 22 urges the pistons 24 axially outwardly and engages the ring with the friction members to apply the brake. n the other hand, if the wheel is rotating in the opposite direction, the energizing cylinder 29 operates the main brake applying cylinders by displacing hydraulic fluid medium in the cylinder 32. Thus, regardless of whether the wheel is rotating in a forward or reverse direction, the main brake actuating wheel cylinders are operated through the energizing unit 28.

Thecontrol unit l2 comprises a reservoir 44 for hydraulic fluid medium and a master cylinder 45. In the present instance, the reservoir and master cylinder are shown as a single unit, although it will be understood that the reservoir may be divorced from the master cylinder, if desired. As shown particularly in Figure 3 of the drawings, the reservoir 44 is of suflicient capacity to provide a space 46 above the normal level 41 of the hydraulic fluid medium to enable expansion of the fluid due to absorption of heat during brake application. It will also be noted that the reservoir is vented to the atmosphere and for accomplishing this result, a plug 48 is threaded in an opening 49 formed in the top wall of the reservoir. The plug 48 is formed with a passage 50 having a reduced and communicating with the atmosphere and having an enlarged end communicating with the interior of the reservoir. The enlarged end is protected by a screen 52 having a cup-shaped retainer 53 secured to the top surface thereof and forming a support for a ball valve member 54. The diameter of the ball 34 is substantially less than the internal diameter oi the enlarged portion ll of the passage to normally enable free flow of" air through the passage 50. However. the diameter of the ball is greater than the internal diameter of the reduced end portion of the passage so that, ii for any reason, the reservoir is inverted, the ball 54 engages the annular shoulder SI surrounding the reduced portion 50 of the passage to close the latter. The reservoir may also be fllled through the opening 49 by removing the plug 43 and the level of the hydraulic fluid medium in the reservoir may be determined by providing an overflow passage 56.

The master cylinder 45 comprises a cylinder 51 having a port 58 at the lower end adapted to be connectedto a port 59 in the energizing wheel cylinder 29 by a conduit 60. A combined piston and valve assembly 6| is slidably supported in the cylinder 51 and is connected to a manually operable control member 62 by means of a tube 63. The upper end of the tube 63 is threaded for connection to a fitting 64 having the upper end coupled to the control member 62 and having a ,port 65 communicating with the interior of the tube through a passage 66 in the fltting 64. The port 55 also communicates with one of the end cylinders 22 through the medium of a conduit 61 and a port 68 formed in the end cylinder 22.

The lower end of the tube 63 is closed by a cap 69 having an upwardly projecting cylindrical portion Ill telescopically engaging the lower end of the tube and welded, or otherwise permanently secured, to the latter. The cap 69 forms a part of the combined piston and valve assemblies BI and is also provided with a downwardly extending portion ll of reduced diameter. The reduced portion forms an annular seat 12 on the cap 69, which is adapted to abut the top surface 13 of an annular piston 14. The piston I4 is slidably mounted on the reduced portion H of the cap 99 and the outer surface of the piston slidably engages the inner wall of the cylinder 51.

The upper end of the piston is reduced to form an annular shoulder 15 intermediate the ends of the piston and this shoulder is adapted to engage a stop 16 to limit upward movement of the piston in the cylinder 51. The stop 16 is in the form of a washer clamped in place between the reservoir and cylinder. The sleeve 63 is normally maintained in its uppermost position by means of a coil spring 11, which surrounds the sleeve in the reservoir 44. The upper end of the spring abuts a collar 18 permanently secured to the sleeve 63 and the lower end of the spring rests on the washer 16. Thus, it will be noted that the spring 11 normally urges the collar I8 against an annular shoulder 19 formed on the top wall of the reservoir 44. In this extended position of the tube 63, the surface 12 on the cap 69 and the surface I3 at the upper end of the piston I4 are spaced from each other to enable hydraulic fluid medium in the reservoir to flow therebetween into an axial passage 83 formed in the reduced portion 1| on the cap 69. In this connection it will be noted that the annular surface of the reduced portion ll of the cap joining the radially extending surface I2 is reduced to cooperate with the adjacent surface of the piston 14 to form an axial passage 8|. The passage 8| communicates with the passage through the medium of ports 82 formed in the reduced portion ii.

The lower end of the passage 8|! is closed by a cap 83 secured to the reduced portion 1| by 5 means of a pin N and having a radially outwardly extending flange 85 which forms a seat for a sleeve '6. The sleeve 08 is slidably mounted on the reduced portion 11 of the cap 69 and is counter-bored to form with the reduced portion an annular chamber 81 which communicates with the passage 80 through a series of circumferen 6 movement of the fitting II and associated tube 11 on the cap 69 and the inner wall of the cylinder 51. The upper end of the sleeve is resilient- 1y held in engagement with the base portion of the sealing ring 89 by means of a coil spring 90 which surrounds the sleeve 86 and is seated at the lower end on the radial flange 85 of the cap 83. The upper end of the coil spring abuts an annular shoulder 9| formed integral with the sleeve, and the strength of this spring is merely suiflcient to prevent a fluttering action of the piston H.

The diameter of'the sleeve is less than the internal diameter of the cylinder to provide an annular passage 92, which communicates at the lower end with the cylinder and communicates at the upper end with the chamber 81 through slots 83 formed in the corresponding end of the sleeve 86.

Attention is now directed to the fact that the reservoir 4| communicates with the interior of 2;

the tube 63 through the medium of vertical ports 85. The ports 95 are formed in the upper end of the cap 89 and extend from the annular surface 12 on the cap to the interior of the tube 62. The arrangement is such that these ports are closed when the surfaces 12 and 13 are in contact. Accordingly, the above surfaces are preferably lapped to prevent any leakage between the same when they are in contact.

It follows from the foregoing that when the several parts of the control unit are in the relative positions shown in Figure 3, communication is established between the reservoir 44 and the main brake actuating cylinders 22. In this connection it will be observed that fluid, from the reservoir is free to flow between the surfaces 12 and 13 through the ports 95 to the interior of the tube 63. Inasmuch as the upper end of the tube 63 communicates with the wheel cylinders 22, it

follows that the latter have a direct communication with the interior of the reservoir. As a result, expansion and contraction of hydraulic fluid medium in the main brake applying unit is compensated for and this unit is maintained in a satisfactory operating condition at all times regardless of wide fluctuations in temperature. It will also be noted that fluid from the reservoir may pass between the surfaces 12 and 13 into the passage 80 through the ports 82. As previously stated, the passage an communicates with the chamber 81 through the ports 88 and the chamber 81 communicates with the lower portion of the cylinder 51. Inasmuch as the lower end of the cylinder 51 communicates with the energizing wheel cylinder 29, it follows that expansion and contraction of hydraulic fluid medium in the energizing unit is also compensated for.

Assuming now that it is desired to apply the brake, the operator merely moves the control member 62 downwardly to effect a corresponding 83. Initial downward movement of the tube Cl against the action of the spring 11 engages the annular surface 12 with the annular surface 13 on the upper end of the piston 14 and thereby eflectively closes the ports 95 as well as the Dessage 81. Thus, communication between the wheel cylinders of both units is not only closed but, in addition, communication between the reservoir and the wheel cylinders of both units is also closed. Continued downward movement of the tube 63 imparts a corresponding downward movement to the combined piston and valve assembly 6|. As a result, hydraulic fluid medium in the lower portion of the cylinder 51 is displaced, efiecting a corresponding displacement of the fluid in energizing wheel cylinder 29. This cylinder applies the brake friction means to the ring 11 and the resulting torque rocks the bracket 21 about the axis of the axle I3 in one direction or the other, depending upon the direction of wheel rotation. Regardless of the direction of rotation of the wheel, the main brake applying unit is actuated by the energizing wheel cylinder to apply the brake in the manner clearly described in connection with the brake assembly.

What I claim as my invention is:

1. Hydraulic operating mechanism comprising a control unit having a reservoir and a master cylinder, said master cylinder having a cylinder provided with a discharge port and having a piston slidably supported in the cylinder, a member for operating the piston extending into the master cylinder and forming a, support on which the piston is also slidably mounted, an annular shoulder on said member providing an annular surface cooperating with a corresponding annular surface on the piston to move the latter in a direction to displace hydraulic fluid medium in the I master cylinder through said port, spring means for normally relatively positioning the member and piston with said annular faces spaced from each other to provide an annular passage therebetween which communicates with the reservoir,

' av passage in said member establishing communication between the annular passage and discharge port in the master cylinder, a second passage in the member communicating with a second discharge port and communicating with the annular passage through a port in said annular shoulder, said first and second passages being closed upon movement of the member against the action of the spring means to engage the coacting annular surfaces aforesaid.

2. Hydraulic operating mechanism comprising a master cylinder having a cylinder open at one end and having a discharge port adjacent the opposite end, an operating member extending into the cylinder through the open end thereof and having a passage therein communicating with a second discharge port, a, piston assembly mounted on the operating member for limited sliding movement relative to the latter and also slidably engaging the cylinder, a reservoir for hydraulic fluid medium surrounding the member above the cylinder, an annular shoulder on the member having a flat annular face cooperating with a flat annular face on the adjacent and of the piston to move the latter in a direction toward the first named discharge port in said cylinder to displace fluid through the latter, spring means for normally relatively positioning the member and piston with the annular surfaces spaced suiilciently from each other to form an annular passage which communicates with the reservoir, a passage connecting the radially inner side or the annular passage to the first named discharge port in said cylinder and a passage extending from the annular face on said shoulder to the passage in said member whereby both discharge ports are connected to the reservoir, said passages being closed to the reservoir upon movement of the member to engage the annular surface on the latter with the adJacent annular surface on the piston.

3. Hydraulic operating mechanism comprising a master cylinder having a cylinder open at one end and having a discharge port adjacent the opposite end through which fluid is discharged to a point of demand, a reservoir for hydraulic fluid medium communicating with the open end of the cylinder, a piston slidable in the cylinder between the reservoir and discharge port, an operating member for the piston connected to the latter for limited sliding movement relative thereto and having a second discharge port through which fluid may also flow to a point vof demand, a passage through the piston for connecting the reservoir to the first discharge port,

'a second passage through the operating member for connecting the reservoir to the second discharge port, cooperating means on said member and piston engageable with one another upon initial movement of the operating member on its pressure stroke to close said passages and to move said piston in a direction toward the first-named discharge port, and means including a spring for urging the member and piston to their inoperative positions and for normally maintaining said operating engaging means in spaced relationship.

4. Hydraulic operating mechanism comprising a master cylinder having a cylinder open at one end and having a discharge port adjacent the opposite end through which fluid, is discharged to a. point of demand, a reservoir for hydraulic fluid medium communicating with the open end of the cylinder, a piston slidable in the cylinder between the reservoir and discharge port, an operating member for the piston having a second discharge port through which fluid may flow to a point of demand and having a passage establishing communication between the second discharge port and reservoir, a passage through the piston for connecting the reservoir to the first named discharge port, and means responsive to initial movement of said member on its compres-- sion stroke to close said passages.

, 5. Hydraulic operatin mechanism comprising a master cylinder having a vertical cylinder open at the top and having a discharge port adjacent the lower end thereof, a reservoir at the upper end of the cylinder communicating with the latter and adapted to contain a hydraulic fluid medium, a piston slidable in the cylinder between the reservoir and discharge port, an operating member extending from the piston through the reservoir and having a second discharge port spaced above the reservoir, a passage in the operating member for connecting the second discharge port to the reservoir, a passage through the piston for connecting the first discharge port to the reservoir, spring means normally urging the piston and operating member to their respective inoperative positions, and means for connecting said passages to the reservoir in the inoperative positions aforesaid of the piston and member and responsive to initial movement of the member on its compression stroke to close said passages.

LUDWIG A. MAJNERI.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,115,230 Oliver Apr. 26, 1938 2,289,525 Swift July 14, 1942 

